On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeD. Appleton, 1909 - 430페이지 |
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9 페이지
... Fertility of varieties when crossed and of their mongrel offspring not universal - Hybrids and mongrels compared independently of their fertility - Summary 219 CHAPTER IX ON THE IMPERFECTION OF THE GEOLOGICAL RECORD On the absence of ...
... Fertility of varieties when crossed and of their mongrel offspring not universal - Hybrids and mongrels compared independently of their fertility - Summary 219 CHAPTER IX ON THE IMPERFECTION OF THE GEOLOGICAL RECORD On the absence of ...
16 페이지
... fertility of varieties when intercrossed ; and fourthly , the imperfection of the Geological Record . In the next chapter I shall consider the geological succession of organic beings throughout time ; in the eleventh and twelfth , their ...
... fertility of varieties when intercrossed ; and fourthly , the imperfection of the Geological Record . In the next chapter I shall consider the geological succession of organic beings throughout time ; in the eleventh and twelfth , their ...
20 페이지
... fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding ...
... fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and plants , though often weak and sickly , yet breeding ...
26 페이지
... fertility of varieties when crossed , -a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of ...
... fertility of varieties when crossed , -a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of ...
34 페이지
... fertile . I can state this from my own observations , purposely made , on the most distinct breeds . Now , it is difficult , perhaps impossible , to bring forward one case of the hybrid offspring of two animals clearly distinct being ...
... fertile . I can state this from my own observations , purposely made , on the most distinct breeds . Now , it is difficult , perhaps impossible , to bring forward one case of the hybrid offspring of two animals clearly distinct being ...
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accumulated adapted affinities allied species America analogous ancient animals appear archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species divergence domestic doubt embryo endemic existing exterminated extinct extremely facts favourable fertilised fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate larvæ laws less living males mammals manner migration modification modified descendants natural selection naturalists nearly nest occasionally offspring organic organisation origin of species perfect pigeons plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary seeds sexual sexual selection Silurian slight sometimes South America sterility structure struggle successive supposed swimbladder tend theory variability variations varieties vary whole widely